The present invention relates to a method of making a shaped body. More particularly this invention concerns the production of such a shaped body by cold and hot pressing.
It is known to form a nonswelling mass into a so-called preform body by a so-called cold pressing operation. The mass from which the body is formed normally consists of a fiber filler with which is mixed a thermosetting synthetic-resin binder. In the cold-pressing operation the mass is pressed at a temperature below the setting temperature, that is the temperature at which the resin begins to cure.
It is common practice to then apply to at least a portion of the surface of such a preform body a skin. One or more foils can constitute this skin. In the case of a decorated body it is common practice to apply first a foil bearing the desired pattern or decoration, then to apply over it a transparent protective foil. Thereafter the body and skin are placed in a hot press wherein the assembly is pressed at a temperature well above the setting temperature in order to cure the binder and bond the skin to the preform body.
Such a method is used for production of interior and exterior construction elements, furniture parts, counter tops, and the like. The resin used to bond together the fibers in the preform body which gives the finished shaped body its structural strength are of the nonswelling type, by which is meant that no foaming or increase in volume takes place when the mass is heated. Typically the nonswelling mass consists mainly of lignocellulose-containing fibers such as comminuted and dried woodchips, sugarcane fibers, and the like. They are mixed with a thermosetting synthetic resin such as a melamine-urea-formaldehyde, or phenolformaldehyde resin. It is also possible to use instead of the wood or sugarcane fibers glass fibers, mineral wool, or asbestos fibers alone or mixed together even with the addition of organic binders. The skin is normally formed, as mentioned above, of two foils. The under or decorated foil is a simple paper or a synthetic-resin sheet bearing the desired pattern. The transparent covering sheet or foil is normally a so-called clear overlay consisting of an unsubstituted alphacellulose paper or a glass fiber web which is saturated with a thermosetting synthetic resin normally of a melamine base. It is also simply possible to provide a thick resin coating on the decor or patterned foil.
It is absolutely essential in such shaped bodies that the skin adhere over its entire surface to the preform body to which it is hot-pressed. However, it is common experience that the transparent protective layer is not flowed smoothly over the entire surface to be covered of the preform body. Another common occurrence is that the skin does not adhere at all to the underlying core constituted by the preform body at some locations.